In general, a light-sensitive (photographic) material comprises a support made of a plastic film base and various layers provided thereon. The layers include an undercoating layer, a backing layer and photographic layers such as a light-sensitive layer, an intermediate layer and a protective layer.
In the present specification, not only the light-sensitive material having the photographic layers but also the so-called "photographic base" (i.e., a support having an undercoating layer) are referred to as the term "photographic film".
The support of the photographic film is generally made of cellulose triacetate film base. The film base is usually prepared by a fluid film forming method (cf., Japanese Patent Publication No. 45(1970)-9074). The method comprises the steps of dissolving cellulose acetate which contains bound acetic acid in an amount of 60 to 62% together with a plasticizer in a solvent such as a mixture of methylene chloride and methyl alcohol to form dope; filtrating and defoaming the formed dope; spreading the dope on a continuously moving support such as a metallic drum and an endless band; and evaporating the solvent.
An undercoating layer can be provided on the surface of the support. The undercoating layer has a function of increasing the adhesion force between the support and photographic layers such as a light-sensitive layer. The undecorating layer may also be provided between the support and a backing layer. The backing layer functions as an antistatic backing, an anticurl backing, a matt backing and an antihalation backing.
The undercoating and backing layers can be prepared by coating a solution of the components of the layers on the surface of a support. The solvent of the solution is preferably so selected that the support swells in the solvent or is partially dissolved in the solvent. If such a solvent is used, the coated components penetrate into the support, and the layers tightly bind the support because the components function as an anchor.
By the way, the recycling recently is of global importance for the saving of natural resources and the protection of environment. The support of the photographic film is not changed through exposure and development. Therefore, the support can be recycled by recovering it from the used photographic film and reusing it as a raw material of a new photographic film.
A few processes for recovering a support from a photographic film have been known.
Prior to the recovering process, the photographic films are collected from the manufacturer, processor and various users of the film. For example, the waste from a film factory contains photographic films which are residual products produced before or after the process of coating photographic layers on a support. Further, a hospital, a motion picture company, a broadcasting station and a processing laboratory dump used photographic films in bulk. The collected films are cut into tips one to several centimeters square for the recovering process.
One of the known processes comprises the steps of important the tips of the film in an aqueous solution containing a protease to remove gelatin layers such as photographic layers (e.g., a light-sensitive layer) and an undecorating layer from the support, washing the tips with water, and optionally extracting and removing dyes from the tips by using a solvent such as a mixture of acetone and methanol, if the tips are colored. The tips are then washed again with water and dryed. The reproduced tips are used for the preparation of a support of a photographic film or the other materials.
Another known process is described in Japanese Patent Provisional Publication No. 53(1978) 15829, which relates to an improvement of a process for recovering a support made of cellulose triacetate film base from a photographic film which comprises the support and a backing layer and/or an undercoating layer containing a synthetic polymer compound having a molecular weight of not less than 5,000 provided thereon. The improvement is that the film is pretreated with an organic solution containing at least one organic solvent in which the cellulose triacetate film base is dissolved or swells or with a solution of an inorganic acid. This process is effective in recovering a support from a photographic film which comprises the support and a backing layer and/or an undercoating layer containing a synthetic polymer compound, which is used for highly improving the quality of the photographic film.